1,720,985 research outputs found
Mechanism-based inactivators of plant copper/quinone containing amine oxidases
No full textCopper/quinone amine oxidases contain CuII and the quinone of 2,4,5-trihydroxyphenylalanine (topaquinone; TPQ) as cofactors.
TPQ is derived by post-translational modification of a conserved tyrosine residue in the protein chain. Major advances have
been made during the last decade toward understanding the structure/function relationships of the active site in Cu/TPQ amine oxidases
using specific inhibitors. Mechanism-based inactivators are substrate analogues that bind to the active site of an enzyme being
accepted and processed by the normal catalytic mechanism of the enzyme. During the reaction a covalent modification of the
enzyme occurs leading to irreversible inactivation. In this review mechanism-based inactivators of plant Cu/TPQ amine oxidases
from the pulses lentil (Lens esculenta), pea (Pisum sativum), grass pea (Lathyrus sativus) and sainfoin (Onobrychis viciifolia,) are
described. Substrates forming, in aerobiotic and in anaerobiotic conditions, killer products that covalently bound to the quinone
cofactor or to a specific amino acid residue of the target enzyme are all reviewed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Reversible thermal inactivation and conformational states in denaturantguanidinium of a calcium-dependent peroxidase fromEuphorbia characias
No full textThe changes in the heme environment and overall structure occurring during reversible thermal inactivation and in denaturant guanidinium of
Euphorbia characias latex peroxidase (ELP) were investigated in the presence and absence of calcium ions. Native active enzyme had an absorption
spectrum typical of a quantum-mixed spin ferric heme protein. After 40 min at 60 ◦C ELP was fully inactivated showing the spectroscopic behavior
of a pure hexacoordinate low-spin protein. The addition of Ca2+ to the thermally inactivated enzyme restored its native activity and its spectroscopic
features, but did not increase the stability of the protein in guanidinium. It is concluded that, in Euphorbia peroxidase, Ca2+ ion play a key role in
conferring structural stability to the heme environment and in retaining active site geometry
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
The reaction mechanism of plant peroxidases.
No full textThe catalysis of class III plant peroxidases is described based on the reaction scheme of horseradish peroxidase. The mechanism consists in four distinct steps: (a) binding of peroxide to the heme-FeIII to form a very unstable peroxide complex, Compound 0; (b) oxidation of the iron to generate Compound I, a ferryl species with a π-cation radical in the porphyrin ring; (c) reduction of Compound I by one substrate molecule to produce a substrate radical and another ferryl species, Compound II; (d) reduction of Compound II by a second substrate molecule to release a second substrate radical and regenerate the native enzyme. Under unfavourable conditions some inactive enzyme species can be formed, known as dead-end species. Two calcium ions are normally found in plant peroxidases and appear to be important for the catalytic efficiency
Isolation of five different stress-related genes from Euphorbia Characias using the Consensus Degenerate Hybrid Oligonucleotide Primers (CODEHOP) strategy
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